The invention is generally related to an internal shield for use in electro-optic ports, and more particularly, to shields that prevent electromagnetic emissions from optical fiber link modules.
In order to transfer data between computer systems rapidly and reliably, electro-optic data transmission is increasingly being used as the method of choice. Optical fibers provide resistance to electro-magnetic interference, increased security, and increased speed due to a wide potential band width. Optical fibers transmit data from an electro-optical transducer, such as a laser or Light Emitting Diode (LED) to an electro-optical receiver that generates electrical information based upon the signal received. An optical fiber includes a core region that is coated by an annular clad. The core region has an index of refraction greater than that of the clad, so that light is transmitted through the core by total internal refraction. The optical fibers are typically either threaded onto the electro-optical components or latched by the use of connectors such xe2x80x9cSCxe2x80x9d connectors.
State of the art optical links operate at over 1000 Mbits/second that generates very high electromagnetic emissions in the range of 100 MHZ-5 GHz. FCC regulations constrain the field strength of radiated emission from certain unintentional radiators such as personal computers, CPU boards, power supplies, and peripherals. FCC regulations provide that the radiated emission from such unintentional radiators at a distance of three meters shall not exceed the following values:
In order to limit such emissions, external shielding has been used around the electro-optical component of such optical links. These shields provide an opening that allows threaded or xe2x80x9cSCxe2x80x9d type connectors to attach to the electro-optical components. Since these connectors are typically plastic they do not serve as a shield to emissions. This electromagnetic xe2x80x9cholexe2x80x9d in the shield allows electromagnetic inference to escape the shielded area and may cause the equipment to exceed the maximum values provided for radiated emissions as specified by the FCC.
Consequently, a significant need continues to exist in the art for a shield that will block electromagnetic interference from escaping from the shielded area. Specifically, a significant need continues to exist for a cost effective shield that blocks significant amounts of the emissions yet allows quick, easy and reliable connection to the electro-optic component.
The invention addresses these and others problems associated in the art with radiated electromagnetic emissions from electro-optical components in a high speed data transfer system. The present invention provides an internal shield with at least one aperture to allow the connector portion of an electro-optic component to pass through for connection to an optical fiber. By providing an internal shield, electromagnetic interference (EMI) is substantially reduced without interfering with the mechanical connection.
In certain embodiments of the invention, the internal shield includes a thin metallic sheet having an aperture to receive the connector portion of an electro-optical component. In a shield for an input/output device, that includes an optical signal generator and optical signal receiver, the shield may include two bores. The first bore receives the connector portion of the generator and the second aperture receives the connector portion of the receiver.
These and other advantages and features, which characterize the invention, are set forth in the claims annexed hereto and forming a further part hereof. However, for a better understanding of the invention, and of the advantages and objectives attained through its use, reference should be made to the Drawings, and to the accompanying descriptive matter, in which there is described exemplary embodiments of the invention.